|Year : 2011 | Volume
| Issue : 4 | Page : 294-299
An evaluation of nanocomposites as pit and fissure sealants in child patients
S Singh1, RK Pandey2
1 Department of Pedodontics and Preventive dentistry, Mahatma Gandhi Post Graduate Institute, Puducherry, India
2 Department of Pedodontics and Preventive dentistry, King George's Medical University, Lucknow, Uttar Pradesh, India
|Date of Web Publication||21-Oct-2011|
Department of Pedodontics and Preventive Dentistry, Mahatma Gandhi Post Graduate Institute, Puducherry - 605 006
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: Dental caries affects populations of all ages in all the regions of the world, with the child patient being at the highest risk. Fifty percent of the permanent molars are decayed by the age of 12, due to lack of information about protection and occlusal morphology. Pit and fissure sealing undoubtedly plays a fundamental role in preventing occlusal caries. The most common approach to assess the sealing ability of pit and fissure sealants of tooth/restoration is the measurement of dye penetration along the interface. Aims and Objectives: The present study aims to evaluate the microleakage and penetration depth of three different types of dental materials, namely (A) Conventional pit and fissure sealant, (B) Flowable composite, (C) Flowable nanocomposite. Study Design: This in-vitro comparative study comprised of extracted human posterior teeth mounted as blocks. Materials and Methods: In the present study, microleakage and penetration depths of conventional sealants/flowable composite and nanocomposite were measured with the help of a dye under stereomicroscope. Statistical Analysis: A student't' test and Analysis of variance (ANOVA) tests were performed to compare the mean microleakage and penetration depth. Results: Microleakage was found to be highest for the flowable composites, and least for the conventional sealant. The nanocomposite values were intermediate. Penetration depth was highest for nanocomposite and least for flowable composite. Conclusions: According to the results, the nanocomposite was found to be an excellent dental material for penetration in deep pits and fissures, though it exhibits mild microleakage. Hence, it can be recommended for use in pediatric dental patients, as a pit and fissure sealing agent.
Keywords: Microleakage, penetration depth, Pit and fissure sealants
|How to cite this article:|
Singh S, Pandey R K. An evaluation of nanocomposites as pit and fissure sealants in child patients. J Indian Soc Pedod Prev Dent 2011;29:294-9
|How to cite this URL:|
Singh S, Pandey R K. An evaluation of nanocomposites as pit and fissure sealants in child patients. J Indian Soc Pedod Prev Dent [serial online] 2011 [cited 2019 Nov 20];29:294-9. Available from: http://www.jisppd.com/text.asp?2011/29/4/294/86370
| Introduction|| |
Dental caries, the most common intra oral disease affecting mankind, is an infectious transmissible disease, with the child patient being at the highest risk. Primary prevention can reduce this risk. The most recent national surveys during the past several decades on caries incidence and prevalence in pediatric and adolescent groups have shown dramatic reductions in dental caries. In the present era of preventive dentistry, the main avenues available for primary prevention are plaque control, use of systemic / local fluoride and fissure sealants. During the 1920s, two different clinical techniques; prophylactic restoration, and prophylactic odontotomy were used to reduce the extent and severity of pit and fissure caries. The use of polymers as fissure sealants owes its origin to Gore,  who used solutions of cellulose nitrate in organic solvents to fill the surface enamel which was porous due to the action of acids in the saliva. Clinical studies of fissure sealing were initiated by Cueto and Buonocore  by using cyanoacrylates.
The greatest success came with the introduction of Bisphenol A - Glycidyl Methacrylate (Bis-GMA) as a sealant material in the early 1970's developed by Bowen RL et al.  . Finally, visible light was used for curing of pit and fissure sealants. Sealant protection has further been improved with the introduction of dentinal adhesives e.g. bonding agents. It may be possible to provide a caries-free dentition with widespread use of sealants in child patients and adolescents. A variety of pit and fissure sealants are available with new advancements and they possess different qualities. There are two main criteria to measure the efficacy of these pits and fissure sealants: Microleakage at sealant-tooth interface; and, penetration depth of the sealants. The aim of the present study was to compare the microleakage and penetration depth of newer composite materials with conventional sealants.
| Materials and Methods|| |
Extracted maxillary/mandibular premolar teeth without any carious lesion were selected as specimens, having occlusal surfaces with deep, narrow, occlusal pit and fissure system that did not allow proper clinical inspection of caries. A total of forty-five freshly extracted non-carious teeth with deep pits and fissures were selected, cleaned of blood and saliva by passing them through running tap water and using a tooth brush. Calculus and other debris were removed using hand scalers. The sample teeth were then embedded in a synthetic resin of self-curing acrylic resin (DPI-RR), and cleaned with an aqueous slurry of fine flour of pumice with the help of a rubber cup in a slow speed contra-angled handpiece (NAC-EC, NSK). Following pumice prophylaxis, the teeth were rinsed with water jet, and dried with oil free compressed air. The samples were then stored in normal saline at 5°C until subjected to experimental procedure to avoid them from being dehydrated and becoming brittle.
The sample teeth were then distributed at random into three groups of fifteen teeth each, after thorough pumice prophylaxis, and then rinsed and dried.
Group 1 comprised of fifteen teeth specimen, where application of conventional pit and fissure sealants was carried out;
Group 2 consisted of fifteen teeth specimen sealed with flowable composite;
Group 3 included fifteen teeth specimen followed by sealing with flowable nano-composite.
The test specimens in the three different groups were prepared for sealant application. After pumice prophylaxis, rinsing and drying, the occlusal surface of the specimens was treated with 37% phosphoric acid gel (Dentsply) for 30 seconds with the help of a disposable brush, rinsed with distilled water for 10 seconds, and then dried with oil free compressed air. The etched surfaces of enamel at the entrance of each fissure system were examined to assure the frosted appearance. After the enamel etching procedure, various sealants were then applied to the fissure system following manufacturer's instructions. To prevent voids and air entrapment the sealants were gently teased through the fissure with the 0.5 mm tip of a periodontal probe (API) and were then polymerized using a light-cure unit (Optilight LD III, Gnatus) for 40 seconds. In group 2 and group 3, bonding agent was applied to the fissure system with the help of a disposable bristle brush, and was polymerized for 10 seconds (according to manufactures instruction), prior to the application of sealants.
After the placement of different sealant material in the three groups, they were stored in distilled water at room temperature for 24 hours, later on the samples were thermocycled for about 1000 cycles between 5°C and 55°C, with a dwell time of 60 seconds and immersed in 2% fuschin dye for a period of one week. Sectioned samples were evaluated under a Labomed stereomicroscope at a magnification of 10X with a graph paper placed below them. Photographs were taken, and they were individually numbered at the linear measurement of the material and dye penetration within the fissure system, which was recorded from an occlusal surface of the crown towards the dentino enamel junction. The sealing material and dye penetration within the fissure system was measured with the help of Gateway 2000 Computer using the free UTHSCA image tool program.
UTHSCSA image tool program
It is a free image processing and analysis program for Microsoft Windows'95™ or Windows NT™. It has been written in Borland's C++ version 5.02. It has been developed at University of Texas Health Science Centre, San Antonio, Texas, by C. Donald Wilcox, S. Brent Dove, W. Doss McDavid and David B. Geer. Image analysis functions of this program include dimensional and gray scale measurements. Information related to the program can be accessed through World Wide Web at http://ddsdx.uthscsa.edu/
| Results|| |
The test specimens of all the three groups were observed for microleakage and penetration depth.
The examination of the test specimens in the Group 1, Group 2 and Group 3 [Figure 1], [Figure 2] and [Figure 3] showed the microleakage of the sealants, and this was measured with the help of the dye, using UTHSCA image tool program. The mean observations were as shown in [Table 1]. Group 2 had the maximum microleakage (0.85 mm); followed by Group 3 (0.713 mm); and, minimum microleakage (0.574 mm) was found in Group 1 [Figure 4]. Intergroup comparison revealed statistically no significant differences between Group 1 vs Group 2, Group 1 vs Group 3 and Group 2 vs Group 3 [Table 2]. The mean microleakage of Group 2 was significantly higher as compared to Group 1 (P = 0.005), and higher to Group 3 (though the difference was statistically not significant) (P = 0.191) [Table 1] and [Table 2]. Analysis of variance (ANOVA) revealed statistically significant difference in mean microleakage among the three groups under study (P = 0.015).
|Figure 1: Microleakage and penetration depth in sectioned tooth of group 1|
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|Figure 2: Microleakage and penetration depth in sectioned tooth of group 2|
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|Figure 3: Microleakage and penetration depth in sectioned tooth of group 3|
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|Table 1: Showing mean microleakage amongst the different groups during the study|
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|Table 2: Comparison amongst groups for mean percentage penetration during the study|
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After examination of the test specimens in the Group < 1, Group 2 and Group 3 [Figure 1], [Figure 2] and [Figure 3] the percentage penetration of the sealants was measured with the help of UTHSCA image tool program. The mean observations recorded were as shown in [Table 3]. The mean percentage penetration was observed maximum in Group 3 (87.48 ± 9.52) followed by Group 1 (79.73 ± 9.51) and then Group 2 (74.61 ± 9.78), [Figure 5]. The mean percentage penetration of Group 3 was significantly higher as compared to Group 1 (P = 0.001) and Group 2 (P = 0.026), respectively. The mean percentage penetration of Group 1 was higher than that of Group 2; however, was not significant statistically (P = 0.191) [Table 3] and [Table 4]. ANOVA revealed statistically significant differences in mean percentage penetration among the three groups under study (P = 0.003). Intergroup comparison revealed statistically significant differences between Group 1 vs Group 2, Group 1 vs Group 3 and Group 2 vs Group 3 [Table 4].
|Table 3: Showing mean percentage penetration amongst different groups during th study|
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| Discussion|| |
The pit and fissures of the occlusal surfaces of posterior teeth are the most susceptible areas to dental decay. Spolsky V.W.  postulated that approximately fifty percent of all carious lesions in age group of six to fourteen years old children occur on occlusal surfaces. Kelly J E. and Harvey C.R  affirmed that there is a dramatic decline in the prevalence of dental caries in the previous years; still the surveys indicate that occlusal caries represent about fifty percent of the carious attack despite many advances in preventive dentistry. The pit and fissure sealants were introduced to eliminate the geometry that harbors bacteria and to prevent nutrients reaching bacteria in the base of the pits or fissures, recognizing the vulnerability of occlusal surface. Nagono (1960)  reported that forty-two percent of the fissures have a narrow occlusal opening and vary in shape as they progress inwards into the tooth, preventing the entry of the explorer into the larger base of the tissue. The primary clinical property of pit and fissure sealant that affects the sealing in narrow, deep, occlusal fissures is its flowability, as the penetration pertains to viscosity.
Recently invented sealant systems are vastly improved over their precursors in terms of viscosity and penetration depth. Conventional composites were not supposed to be as good pit and fissure sealant as they had high viscosity, however now, the newer low viscosity composites such as flowable composites and nanocomposites have shown sufficient flow. The present study, therefore, aimed at evaluating the efficacy of newer composites as pit and fissure sealants. The selection criteria of sample teeth for the present study were in accordance of Stritikus J and Owens B , Burrow JF, Burrow MF, Makinson OF , Noncarious premolars were chosen as they have adequate occlusal fissure morphology and are the most common teeth indicated for extraction for reasons other than caries; and thus, have their occlusal fissure characteristics preserved.
The samples in each group were subjected to pumice prophylaxis which improves penetration and retention of sealants in deep pits and fissures, as suggested by Ansari G, Oloomi K, Eslami B.  This was followed by acid etching for 15 to 60 seconds to produce adequate sealant bonding while minimizing the loss of surface enamel. In the present study, bonding agent used in group 2 and group 3 was polymerized for 10 seconds. The use of dentin bonding agent increased the sealant retention in teeth even when salivary contamination occurred. The present study confirms the finding of Feigel, Hitt and Spleith  who had used the dentin bonding agents.
Sealant materials were placed in the three groups, and polymerized by conventional halogen curing light for minimum of forty seconds (as per manufacturer instructions). Stritikus J and Owens B  evaluated the microleakage of sealants and resin restorations utilizing two different curing lights. The conventional Ortholux curing light (OCL) and the Plasma Arc Curing (PAC) light attached to the KCP air abrasion unit of American Dental Technologies were utilized to polymerize sealants and resin restorations on extracted third molars and premolars. According to this study, it appears that PAC light would be best utilized to cure sealants and/or possibly polymerize orthodontic brackets. The conventional curing light appears to remain the best choice for polymerizing class I composite restorations.
The differences in thermal expansion between the sealant and tooth structure, coupled with polymerization shrinkage of sealant leads to marginal gap formation at the sealant-tooth interface; and, thermocycling effect, which induces a thermal stress in in vitro that simulates the oral environment that may be present during the service period of a sealant. In the present study, samples were thermocycled between 5°C and 55°C, so as to maintain a difference of 49°C, which approximates the maximum temperature range measured in vivo, as demonstrated by Simmons et al. 
Samples were then kept in 2% fuschin dye for one week as suggested by Gillet D. et al.  and then sectioned in a mesiodistal/buccolingual direction to observe the sealant material and dye penetration under the stereomicroscope with attached digizoom camera with the help of dye and UTHSCA Image Tool Program. Pardi V, Sinhoreti MA, Pereira AC, Ambrosano GM, Meneghim Mde C.  adopted a similar technique for observation. In the present study, it was observed that the conventional sealant showed less microleakage than flowable composite.These findings are supported by the studies of Francescut P, Lussi A  and Kwon HB, Park KT  who evaluated the microleakage and penetration depth between conventional sealant and flowable composite. Among the two composites namely flowable composite and nanocomposite, there was a difference in the level of mean microleakage [Table 1]; however, this difference was not significant statistically [Table 2], confirmed by the studies of Known HB, Park KT.  and supported by Radal M  which states that though pit and fissure sealants provide good sealing ability but their consistency is not of prime importance. Gillet et al. on his study found no difference in microleakage and penetration depth using flowable composite and hybrid composite, and this seems contradictory to the finding of the present study.
In the present study, nanocomposite showed better penetrating ability in deep pit and fissures as given in [Table 3]. This result was confirmed by the findings of Kakaboura et al.  who evaluated the penetration ability of a flowable composite resin and a flowable compomer, applied with and without their bonding agents in comparison to an unfilled resin. He concluded that the penetration ability of all sealants was higher in shallow/wide fissures than in narrow/deep fissures. Thus, optimal dental health can be achieved by sealing deep pits and fissures with the help of sealant, which have the ability of less microleakage and deeper penetration in deep pits and fissures, like nanocomposite restorative materials.
| Conclusions|| |
The present study led to the following conclusions:
The present study revealed that the nanocomposite was found to be an excellent dental material for penetration in deep pits and fissures, though it exhibits mild microleakage. Hence, it can be recommended for use in pediatric dental patients, as pit and fissure sealants, which is a core strategy for prevention of caries.
- Microleakage of the three different restorative materials used as pit and fissure sealants was found to be higher for flowable composite and least for conventional sealant. The nanocomposite values were intermediate, i.e. flowable composite > nanocomposite > conventional sealant.
- Penetration depth of the three different dental materials used as pit and fissure sealant was higher for nanocomposite, and least for flowable composite. The conventional sealant ranks second, i.e. nanocomposite > conventional sealant > flowable composite.
Where, Group 1 comprised of fifteen teeth specimen, where application of conventional pit and fissure sealants was carried out; Group 2 consisted of fifteen teeth specimen sealed with flowable composite; Group 3 included fifteen teeth specimen followed by sealing with flowable nano-composite. [Table 1], [Table 2], [Table 3] and [Table 4]
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2], [Table 3], [Table 4]